A multi-layer piezoelectric element can be obtained, for example, by printing a conductive paste for forming an internal electrode layer onto a ceramic green sheet, laminating a plurality of ceramic green sheets to which the conductive paste has been applied to form a stacked compact, firing the stacked compact to form a sintered stacked body, and performing processing such as grinding processing on the stacked body.
The internal electrode layers are alternately connected to a positive and a negative external electrode. A portion where an internal electrode layer connected to a positive external electrode and an internal electrode layer connected to a negative external electrode adjacent thereto overlap each other in a stacked direction of the stacked body functions as an active portion. With the application of a voltage, piezoelectric layers in this active portion are extended and contracted during driving. Furthermore, in the stacked body, inactive portions that do not include an internal electrode layer and are not extended and contracted during driving are arranged so as to sandwich the active portion from above and below. The inactive portions are necessary portions for insulating the end faces from an external jig.
Conventionally, since the inactive portions do not include an internal electrode layer, a crack easily occurs from an end face thereof. Once a crack occurs, the crack extends to the active region and causes a short circuit between electrodes, which results in the problem that the element itself is damaged. Furthermore, the firing contraction coefficient of the inactive layer is different from that of the active layer, which results in the problem that delamination occurs at the boundary there between. In order to address these problems, a counter measure is known in which particles of silver are added in advance to this inactive layer (see Patent Literature 1 below).